JPH10176601A - Crankcase clamping structure for two-stroke internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crankcase clamping structure for a twostroke internal combustion engine, which enables an internal combustion engine together with an associated transmission to be made compact. SOLUTION: A crankcase clamping structure is applied to a two-stroke internal combustion engine which includes at least one cylinder detachably arranged on a crankcase 21 for rotatably supporting a crankshaft. The crankcase 21 is divided at its plane on which the axial center of the crankshaft lies. Clamping bolts 60F and 60R for use in joining both divided crankcases 21U and 21D together and clamping the support part of the crankshaft are arranged so as to be exposed to the outside when a cylinder 22R is detached from the crankcase 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crankcase tightening structure for a two-stroke internal combustion engine.

[0002]

2. Description of the Related Art A crankcase of a two-stroke internal combustion engine is divided into a left and right part divided by a plane perpendicular to the crankshaft and a vertical part divided by a plane including the crankshaft. The internal combustion engine is designed in consideration of the fact that the tightening bolt connecting the two split crankcases is tightened substantially perpendicularly to the split surface of the case.

[0003] A conventional two-sided split crankcase
FIG. 10 shows an example of a stroke internal combustion engine (Japanese Patent Publication No. 44896/94). The internal combustion engine 01 is a V-type three-cylinder internal combustion engine, in which two horizontal cylinders 04, 04 project in front of a crankcase 02 in parallel to the left and right, and one vertical cylinder 05 projects upward. I have.

[0004] The crankcase 02 is formed integrally with the transmission case 03 of the rear transmission 07. The two cases 02 and 03 are surfaces including the crankshaft 06 and are horizontal planes perpendicular to the axis of the vertical cylinder 05. Is divided into upper and lower parts as a case division plane X. Tightening bolts 010 for connecting the upper and lower split crankcases 02U and 02D and tightening the support portion of the crankshaft 06 penetrate upward from below the lower split crankcase 02D and are screwed into the upper split crankcase 02U. And tightened.

[0005] In a transmission case 03 which is divided into upper and lower parts, a main shaft disposed on a case division plane X is provided.
08 and the counter shaft 09 are stored. That is, the crankshaft 06, the main shaft 08, and the countershaft 09 are sequentially rotatably sandwiched and supported by upper and lower cases along the case division plane X.

As described above, the front of the crankcase 02 is the horizontal cylinders 04, 04, the upper is the vertical cylinder 05, the rear is the transmission 07, the lower is the tightening side of the tightening bolt 010, and the lower is the space for the tightening work. Must be kept.

An intake system mechanism 011 is formed integrally at the front diagonally upper part of the crankcase 02, an exhaust system mechanism 012 of the horizontal cylinders 04 and 04 is formed at the front diagonally lower part, and a vertical cylinder 05 is formed at the rear diagonally upper part. Exhaust system mechanism 013
Is formed, and a transmission 07 extends obliquely below the rear side.

[0008]

In the internal combustion engine 01, a work space must be secured below the crankcase 02 for tightening the tightening bolts 011. Therefore, the transmission 07 is inevitably mounted on the crankcase 02. Of the cylinder 04, the crankshaft 06,
With the structure in which the main shaft 07 and the counter shaft 08 are arranged in front and rear, the front and rear length of the internal combustion engine 01 including the transmission 07 is large.

There is no room to provide a balancer or the like disposed in the width direction in the vicinity of the crankshaft 06. Only the lower part of the transmission 07 can be considered as the disposition position of the balancer, but if it is provided avoiding the tightening bolt 010, it will be located far from the crankshaft 06.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a crankcase tightening structure of a two-stroke internal combustion engine which can make the internal combustion engine including the transmission compact.

[0011]

In order to achieve the above object, the present invention provides a two-stroke internal combustion engine in which at least one cylinder is detachably mounted on a crankcase that rotatably supports a crankshaft.
When the crankcase is divided at the plane including the axis of the crankshaft and the cylinder is removed from the crankcase,
A crankcase tightening structure for a two-stroke internal combustion engine is provided in which the two split crankcases are combined and a tightening bolt for tightening the crankshaft support portion is arranged to face the outside.

When the cylinder is removed from the crankcase, the tightening bolt is arranged so that the tightening bolt faces the outside. Therefore, the tightening position of the tightening bolt can be set narrower than the cylinder cross section, and the internal combustion engine can be set. Can be reduced in size. In addition, the tightening by the tightening bolts can be performed from the cylinder side, so that the other side on the side opposite to the cylinder has a large degree of freedom in arranging other components, thereby making the internal combustion engine compact.

According to a second aspect of the present invention, in the crankcase tightening structure for a two-stroke internal combustion engine according to the first aspect, the case divided surfaces of the two split crankcases are substantially perpendicular to the axis of the cylinder. Is what it is. The tightening bolts connecting the two split crankcases can be tightened in a direction substantially perpendicular to the split surface of the case, and secure fastening can be performed.

According to a third aspect of the present invention, there is provided the two-stroke internal combustion engine according to the first or second aspect, wherein the bolt tightening seat surface of the tightening bolt faces the mating surface of the crankcase with the cylinder. It is a case fastening structure. It is easy to form a concave portion on the mating surface of the crankcase with the cylinder and perform the seating process.

According to a fourth aspect of the present invention, in the two-stroke internal combustion engine according to the first or second aspect, a bolt tightening seat surface of the tightening bolt is located inside a mating surface of a crankcase and a cylinder. This is a crankcase tightening structure provided in the intake passage or the scavenging passage.

By using a suction passage or a scavenging passage inside the mating surface of the crankcase and the cylinder, that is, in the crankcase, a bolt mounting seat surface is provided in the middle thereof, so that the tightening position is made closer to the cylinder axis. Therefore, the size of the internal combustion engine can be further reduced.

According to a fifth aspect of the present invention, there is provided the second aspect of the first aspect.
In the stroke internal combustion engine, the one split crankcase has a balancer shaft, and the balancer shaft has a crankcase tightening structure disposed on an extension of the tightening bolt and parallel to the crankshaft. By disposing the balancer shaft parallel to the crankshaft on the extension of the tightening bolt, the balancer shaft can be made as close as possible to the crankshaft, and the entire internal combustion engine can be made compact.

According to a sixth aspect of the present invention, there is provided a two-stroke internal combustion engine according to any one of the first to fifth aspects, wherein the plurality of cylinders are arranged in a V-shape. A crankcase in which a plurality of cylinders are arranged in a V-shape is divided by a case division plane that is substantially perpendicular to the axis of one cylinder, and tightening with a tightening bolt is performed from the cylinder side. A large degree of freedom in arranging other components can be ensured even in a V-type internal combustion engine, and the internal combustion engine can be made compact.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall side view of a motorcycle 1 equipped with an internal combustion engine 20 according to the present invention.
Shown in

A pair of left and right main frames 3 extend obliquely downward from the head pipe 2 rearward, and a front wheel 5 is pivotally supported at a lower end of a front fork 4 rotatably supported by the head pipe 2. The upper end of the steering shaft 6 extending upward integrally forms a steering wheel 7 by expanding left and right.

A front end of a swing arm 9 is pivotally supported by a pivot 8 at a rear end of the main frame 3, and a rear wheel 10 is pivotally supported at a rear end of the swing arm 9 extending rearward. Rear wheel
A seat 11 supported by a seat rail extending slightly obliquely upward from the main frame 3 to the rear is provided above the main frame 3, and a fuel tank 12 supported by the pair of main frames 3 is provided in front of the seat 11. ing.

An internal combustion engine 20 is provided below the fuel tank 12 and suspended from the main frame 3. The internal combustion engine 20 is a two-cylinder V-type spark ignition type two-stroke internal combustion engine.
, 22R project forward in a V-shape (for example, at an included angle of about 100 degrees) when viewed from the side, and an exhaust pipe 23L extends rearward from a lower portion of a left cylinder 22L projecting obliquely downward and toward the right side of the vehicle body. The exhaust pipe 23R extends downward from the front side of the right cylinder 22R, which projects diagonally upward, and extends downward from the front side of the right cylinder 22R, which extends to the right side of the rear wheel 10 to the rear of the rear wheel 10 and also to the right side of the rear wheel 10. Connected to the muffler 24R.

A reed valve 25 (FIG. 2) is mounted on the upper part of the crankcase 21 behind the right cylinder 22R projecting obliquely upward.
The intake pipe 26 is connected to the extension carburetor 27 via the carburetor 27. The crankcase 21 integrally includes a transmission chamber 31 behind the crankcase 30 (see FIG. 2), and a countershaft 38 projecting leftward from the transmission chamber 31 and a rear wheel.
A chain 15 is bridged between the vehicle 10 and the vehicle 10 via a sprocket. A radiator 16 is provided in front of the internal combustion engine 20, and a cooling water pipe 17 extending from a lower portion of the radiator 16.
Is connected to the lower left side of the crankcase 21.

The crankcase 21 is a plane including the crankshaft 32 and an oblique plane that is substantially perpendicular to the axis of the right cylinder 22R.
It is divided into two parts, 21U and lower crankcase 21D.
As shown in the figure, the transmission chamber 31 is formed by partitioning the lower crankcase 21D from the crank chamber 30 by a partition wall 21a.

As shown in FIG. 3, the crank chamber 30 is partitioned by partition ribs 30U and 30D corresponding to the left and right cylinders 22L and 22R. The left and right side walls of the upper crankcase 21U and the case dividing plane X of the partition rib 30U. And lower crankcase
Semicircular notches are formed corresponding to the case division plane X of the partition ribs 21D and the partition ribs 30D, respectively, so that the bearings 33, 34, and 35 of the crankshaft 32 are held therebetween.

Mission chamber 31 of lower crankcase 21D
Are inserted from the right side in a state where the transmission 36 such as the main shaft 37, the countershaft 38, and the shifter 39 is combined with the upper and lower crankcases 21U and 21D. Mission room with right cover 41 detachably mounted on the right side
31 is closed and the left end of each shaft is the lower crankcase 21D
The right end is supported by the bearing of the right cover 41.

The crankshaft is located in front of the main shaft 37.
A balancer shaft 40 is provided below the position 32 in parallel with the crankshaft 32. Crankshaft 32, each cylinder 22L
, 22R, the movement of the piston 45 reciprocating is transmitted via the connecting rod 46 to rotate.

Referring to FIG. 3, the left end of crankshaft 32 has A
A C generator 47 is provided, and one of the two gears 48 and 49 fitted to the right end meshes with a gear 50 rotatably supported by the main shaft 37 to rotate the gear 50. The power is transmitted to the main shaft 37 via the clutch 51. Referring to FIG. 7, the other gear 49 meshes with a gear 52 having a balancer weight 52a fitted to the balancer shaft 40 to rotate the balancer shaft 40.

The cylinders 22L and 22R cover the cylinder bores, respectively, and the cylinder heads 28L and 28R are fixed by bolting, and the cylinder walls have exhaust pipes 23L and 22R.
One exhaust port 22a leading to 22R and crank chamber 30
A total of five scavenging ports 22c, which are openings of a scavenging passage 22b communicating with the exhaust port 22a, are formed at right and left sides of the scavenging passage 22b (see FIG. 4).

As described above, the crankcase 21 is formed by the upper crankcase on the case division plane X at the crankshaft 32.
21U and a lower crankcase 21D are divided into two parts. The two parts are connected to each other, and six tightening bolts 60 are tightened to clamp the bearings 33, 34, 35 of the crankshaft 32.

As shown in FIG. 4, the tightening bolt 60 is substantially perpendicular to the case division plane X, and
Upper crankcase 21U from bolt tightening seat surface 61F, 61R of U
And screwed into the female screw portion of the lower crankcase 21D and tightened. When four of the six bolts 60 are located on the right cylinder 22R side and the right cylinder 22R is mounted on the upper crankcase 21U, the bolt heads are hidden. It is in.

FIG. 5 is a view of the upper crankcase 21U viewed from the mating surface with the right cylinder 22R. The cylinder sleeve 22Ra protruding from the mating surface of the right cylinder 22R is provided inside the substantially rectangular frame-shaped mating surface 21Ua. 21Ub into which is inserted
Are formed, and large notches 21Uc and 21 are formed on the left and right of the circular hole 21Ub.
Uc and a notch 21Ud are cut out on the rear side, and the scavenging passage 22b is formed outside the cylinder sleeve 22Ra of the notches 21Uc, 21Uc, and 21Ud.

A circular hole is formed on the left and right in the front part of the substantially rectangular frame-shaped mating surface 21Ua, and the bottom surface thereof is used as a bolt tightening seat surface 61F, and a bolt through hole is formed at the center of the bolt tightening seat surface 61F. 62F, 62F are formed. Mating surface 21Ua
Since the bolt tightening seat surfaces 61F, 61F are formed in the seat, machining of the seat surface is easy. At the front side of the mating surface 21Ua, right and left bolt tightening seat surfaces 61F, 61F
Are provided with bolt holes 63F, 63F. Two cooling water passages 66, 66 are provided between the left and right front bolt fastening seat surfaces 61F, 61F.

On the other hand, bolt holes 63R, 63R for mounting the right cylinder 22R are formed on the left and right sides of the rear surface of the mating surface 21Ua. The bolt fastening seat surfaces 61R, 61R are formed at a predetermined depth from the mating surface 21Ua, bulging to the inner side of the substantially rectangular frame-shaped mating surface 21Ua, and to the rear of the notches 21Uc, 21Uc. The bolt fastening seat surfaces 61R, 61R are provided with bolt through holes 62R, 62R.

As described above, the front bolt fastening seat surfaces 61F, 61
F faces the mating surface 21Ua, and the rear bolt tightening seat surfaces 61R, 61R
R is provided further inside than the substantially rectangular frame-shaped mating surface 21Ua, and the four bolt tightening seat surfaces 61F, 61F, 61R, 61R are located at substantially square corners surrounding the cylinder sleeve 22Ra, and The distance between them is kept small by approaching 22Ra. Especially, the rear bolt tightening seat surfaces 61R, 61R are located in the middle of the scavenging passages 22b, 22b formed by the notches 21Uc, 21Uc and substantially below the cylinder sleeve 22Ra. It is located in.

Tightening bolts 60 are inserted into the front bolt through holes 62F, 62F.
F and 60F into the rear bolt through-holes 62R and 62R.
R and 60R are respectively inserted from the mating surface 21Ua side and penetrated, screwed into the female screw portion of the lower crankcase 21D, and tightened between the bolt tightening seat surfaces 61F, 61F, 61R and 61R. As shown in FIG. 5, the upper crankcase 21U has two bolt fastening seat surfaces 64F and 64R formed on the outer surface thereof together with bolt through holes 65F and 65R, and the fastening bolt 60 is inserted from the outside. Be tight.

Thus, the tightening bolts 60F, 60F, 60R, 60
Since the tightening positions by R are set narrower to each other, the size of the internal combustion engine 20 can be reduced. Upper crankcase 21
When the right cylinder 22R is mounted on U, the mating surface 21Ua and the inside thereof are covered, and the bolt tightening seat surfaces 61F, 61F, 61
Since R and 61R are also shut off from the outside, the bolted seat surface 61F,
There is no need to consider the 61F, 61R, and 61R seals.

Since the tightening bolts 60F and 60R are inserted from the right cylinder 22R side and tightened, a space is formed on the side of the crankcase 21 opposite to the right cylinder 22R where other parts can be freely arranged. The internal combustion engine 20 includes a transmission 36, and a balancer shaft 40 is disposed in parallel with the crankshaft 32, particularly on an extension of the front tightening bolt 60F (FIG. 4). reference).

As shown in FIG. 4, the balancer shaft 40 can be brought as close as possible to the crankshaft 32.
It is possible to make 20 compact. That is, in the internal combustion engine 20, the cylinders 22L and 22R are arranged in a V-shape. Referring to the arrangement of parts around the crankshaft 32, referring to FIG. The cylinders 22L and 22R are located at 10 o'clock, the intake system is located at 1 o'clock, the transmission 36 is located at 3 o'clock, and the tightening bolts 60F and 60R are the same as the right cylinder 22R.
It is screwed in from the time direction.

Therefore, parts can be arranged on the opposite side of the right cylinder 22R with respect to the crankshaft 32, that is, at 4 o'clock or 5 o'clock, and a part of the transmission 36 and the balancer shaft 40 can be arranged. It is possible to dispose it close to the shaft 32. As described above, the components of the internal combustion engine 20 are efficiently arranged around the crankshaft 32, and the overall size of the internal combustion engine 20 is reduced.

If the tightening bolt is screwed in from below as in the prior art, parts cannot be arranged in the 4 o'clock or 5 o'clock direction, and the balancer shaft and the like must be arranged in another place. The distance from the crankshaft, making compactification difficult.

The mating surface 21Ua of the upper crankcase 21U of the upper and lower crankcases 21U, 21D coupled as described above.
As shown in FIG. 6, the right cylinder 22R is abutted and is fixed by four bolts 70 using bolt holes 63F and 63R. The left cylinder 22L is brought into contact with a mating surface that straddles the upper and lower crankcases 21U and 21D, and is fixed by bolts 71.

A cylinder fastening boss 72 having a bolt hole in the lower crankcase 21D where the bolt 71 is screwed is
The side of FIG. 6 overlaps with the balance weight portion 40a of the balancer shaft 40. As shown in FIG. 7, a notch 72a is formed in the cylinder tightening boss 72 so as not to interfere with the balance weight portion 40a. I try to avoid it.

The balancer shaft 40 has a cylindrical shape,
A balance weight portion 40a is formed at the left end. The balance weight portion 40a is developed in a semi-disc shape as shown in FIG. 8, and a groove 40b is formed in an end face in a diametric direction. A water pump shaft 81 is fitted into the left end opening of the balancer shaft 40, and a projection 81a protruding from the water pump shaft 81 is provided.
(See FIG. 9) fits into the groove 40b, and the water pump shaft 81 rotates integrally with the balancer shaft 40.

As shown in FIG. 7, an impeller 82 is fitted to a water pump shaft 81 to form a water pump 80. A water pump case 83 rotatably supports the water pump shaft 81 to support the impeller 82. It covers around. The left side opening of the water pump case 83 is covered with a cooling water suction connection pipe 84,
The cooling water pipe 17 extending from the radiator 16 is connected to 84.

A discharge passage 84 is formed around the impeller 82 of the water pump case 83,
As shown by a two-dot chain line, a water jacket 85 is formed. By passing the cooling water through the water jacket 85, the crankcase is cooled, and the constant temperature allows the intake efficiency to be improved and stabilized.

In this embodiment, the upper crankcase 21U
The lower crankcase 21D and the lower crankcase 21D were connected and tightened with a tightening bolt 60, but a stud bolt was screwed into the female thread of the lower crankcase 21D first, and a bolt through hole was used when the upper crankcase was fitted. Alternatively, a nut may be screwed into the exposed portion at the end of the stud bolt, and the nut may be fastened to the fastening seat surface.

[Brief description of the drawings]

FIG. 1 is an overall side view of a motorcycle equipped with an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a side sectional view of the internal combustion engine.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a side view of the internal combustion engine partially omitted.

FIG. 5 is a top view of the upper crankcase.

FIG. 6 is a side view of the internal combustion engine with a part thereof omitted.

7 is a cross-sectional view taken along line VII-VII and line VII'-VII 'in FIG.

FIG. 8 is a side view of the balancer shaft.

FIG. 9 is a side view of a water pump shaft.

FIG. 10 is a side sectional view of a conventional two-stroke internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 2 ... Head pipe, 3 ... Main frame, 4 ... Front fork, 5 ... Front wheel, 6 ... Steering shaft, 7 ... Steering wheel, 9 ... Swing arm, 10 ...
Rear wheel, 11 ... seat, 12 ... fuel tank, 15 ... chain, 16
... radiator, 17 ... cooling water pipe, 20 ... internal combustion engine, 21
… Crankcase, 21U… Upper crankcase, 21D… Lower crankcase, 22L… Left cylinder, 22R… Right cylinder, 23L, 23R… Exhaust pipe, 24L, 24R… Muffler, 25… Reed valve, 26… Intake pipe, 27 ... vaporizer, 28L, 28R ... cylinder head, 30 ... crank chamber, 31 ... mission chamber, 32 ...
Crankshaft, 33, 34, 35 ... bearing, 36 ... transmission, 37 ... main shaft, 38 ... counter shaft, 39 ... shifter, 40 ... balancer shaft, 45 ... piston, 46 ... connecting rod, 47 ... AC generator, 48 , 49,50… gear, 51… clutch, 52… gear, 60F,
60R: Tightening bolt, 61F, 61R: Bolt tightening seat, 62F, 62
R: Bolt through hole, 63F, 63R: Bolt hole, 64F, 64R: Bolt tightening seat, 65F, 65R: Bolt through hole, 66: Cooling water channel, 70, 71: Bolt, 72: Cylinder tightening boss, 80 ... water pump, 81 ... water pump shaft, 82 ... impeller, 83 ... suction connection pipe, 84 ... discharge path, 85 ... water jacket.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshiro Kawai 3-15-1, Izumi, Asaka-shi, Saitama Prefecture Inside Honda Racing Co., Ltd.

Claims (6)

[Claims] 1. A two-stroke internal combustion engine in which at least one cylinder is detachably mounted on a crankcase that rotatably supports a crankshaft, wherein the crankcase is divided by a plane including the axis of the crankshaft. A crankcase tightening structure for a two-stroke internal combustion engine, wherein a tightening bolt for connecting the two split crankcases and tightening the crankshaft support portion faces outward when the cylinder is removed. 2. The crankcase tightening structure for a two-stroke internal combustion engine according to claim 1, wherein a case dividing surface of the two split crankcases is substantially perpendicular to an axis of the cylinder. 3. The two-stroke internal combustion engine according to claim 1, wherein the bolt fastening seat surface of the fastening bolt faces a mating surface of the crankcase with the cylinder. Attached structure. 4. The bolt fastening seat surface of the fastening bolt is provided in the middle of an intake passage or a scavenging passage inside the mating surface of a crankcase and a cylinder. 3. The crankcase tightening structure for a two-stroke internal combustion engine according to 2. 5. The crankshaft according to claim 1, wherein the one of the split crankcases has a balancer shaft, and the balancer shaft is disposed on an extension of the tightening bolt in parallel with the crankshaft. Tightening structure for a crankcase of a stroke internal combustion engine. 6. The crankcase tightening structure for a two-stroke internal combustion engine according to claim 1, wherein a plurality of cylinders are arranged in a V-shape.